An animal model is provided which is genetically engineered to express human serum albumin, and such animals may be advantageously used in assessing drugs, vaccines or other therapeutic compounds that may be used in humans. In addition, an animal model is provided which does not manufacture its own albumin and which has been injected with human serum albumin. Through the use of these animal models, drugs and other chemicals can be more accurately assessed in physiological environments that reflect the conditions to be expected in humans, and such models will be useful in assessing new drugs and evaluating toxic substances for potential dangers as carcinogens, mutagens, etc. Other applications include evaluating immunological properties of various albumin-engineered proteins which might be administered to humans as therapeutics or vaccines, and research of disease states, such as genetic diseases, to provide further insight in treating these diseases.